In the prior art, tennis balls and the like are customarily inflated to a prescribed pressure and are tested in various ways, such as bounce testing, weight uniformity testing, and measuring ball deflection under a prescribed ball compressing force. Despite stringent efforts to inflate balls with great accuracy to predetermined degrees of pressure, followed by careful testing and pressure packaging, tennis balls and racquet balls frequently do not have the correct and uniform bounce and other play characteristics required for tournament play, particularly professional play. Heretofore, the prior art has not been able to deal with the problem of ball uniformity under known methods of manufacturing and testing with complete success despite strenuous efforts toward improvement. One reason for this is that there are too many hidden variables in the materials from which the balls are made, such as wall thickness, thickness uniformity and porosity for complete success ever to be achieved under prior art manufacturing methods.
To comply with the duty of disclosing known prior art under 37 C.F.R. 1.56, the following U.S. Pat. Nos. are made of record herein:
______________________________________ 1,713,755 3,921,977 2,926,705 3,929,174 3,699,739 3,932,977 4,012,041. ______________________________________
In light of the above deficiencies of the prior art and ever-present variables in manufacturing which can never be completely controlled, the present invention involves a totally new approach to inflated ball manufacturing, wherein no effort is made to achieve uniform inflation pressure, but rather in the manufacturing process balls are inflated to such a degree that each ball will precisely resist or balance a given applied compressive force resulting in a given deflection of the ball. In other words, the improved process creates a perfectly uniform stress-strain relationship instead of a uniform inflation pressure in the balls, with the result that all of the balls so manufactured will possess the identical play characteristics, including bounce characteristics, regardless of variations in inflation pressure. Therefore, the improved method avoids the problems of the prior art caused by hidden variables in materials and processing steps and by one simple balanced deflection procedure, the quality of inflated balls produced far exceeds the quality of any known prior art production. The superior results are obtained with economy and simplicity of processing solely by utilizing readily available technology and commercial equipment.
Other features and advantages of the invention will become apparent during the course of the following description.